The present invention relates generally to a hermetic compressor and, more particularly, to such a compressor including an oil sump and a rotatable crankshaft within a housing, wherein the crankshaft has an axial oil passageway through which oil from the oil sump is supplied to remote locations requiring oil.
More specifically, the present invention relates to a hermetic compressor including within a housing a compressor mechanism, i.e., a scroll compressor mechanism, wherein said housing has an oil sump. The compressor mechanism is drivenly coupled to a rotating crankshaft, whereby the mechanism compresses refrigerant fluid for use by a refrigeration system. The rotatable crankshaft is supported within bearings typically requiring lubrication. Accordingly, a lubrication system delivers oil from the oil sump to the bearings for lubrication thereof.
In a typical compressor lubrication system, an axial oil passageway is provided in the crankshaft to provide fluid communication between the oil sump and the bearings and/or other locations requiring oil. Oil from the oil sump is pumped into and through the axial oil passageway by either a differential pressure or centrifugal oil pumping system.
In a differential pressure oil pumping system, a pressure differential between the oil sum and the destination of the oil causes oil to flow through the axial oil passageway. However, several problems arise in such a system due to the relatively large pressure differential experienced. For instance, a high oil flow rate is induced which causes excessive oil leakage into the refrigeration system, thereby resulting in refrigeration system inefficiencies. Efforts to reduce the oil flow rate by throttling the oil delivery passages, i.e., restricting the passages, leads to further problems including clogging of the passageways and very low oil flow rates through the axial passageway. In the event of such restrictions in flow-controlling oil delivery passageways, the differential pressure system experiences oil stack-up in the axial passageway. A slow oil flow rate and oil stack-up can increase the temperature of the oil in the axial oil passageway, thereby causing oil breakdown and possible damage to the bearings.
In a typical centrifugal oil pumping system, an oil pump is operable upon rotation of the crankshaft to pump oil into the axial oil passageway at one end of the crankshaft. The oil flows through the passageway and is then vented through a vent hole located at the other end of the crankshaft. Intermediate the two crankshaft ends, oil is supplied to various locations requiring oil. Such a system is commonly used in certain types of compressors, i.e., reciprocating piston, scotch-yoke, and rotary vane, wherein the vent hole is uncovered and in open communication with the interior of the housing, including the oil sump.
However, a problem can arise when a centrifugal oil pumping system is used in a scroll-type compressor, because the end of the crankshaft having the vent hole is adjacent the bottom surface of the scroll. In such an arrangement, the crankshaft and the orbiting scroll member define a substantially closed fluid chamber with which the vent hole communicates. The closed fluid chamber inhibits venting of the axial oil passageway thereby causing slow oil flow rates and the problems associated therewith. Furthermore, at compressor start-up when the axial oil passageway may be filled with gas, the gas is not as quickly vented out, but is instead required to escape through bearings and the like. Consequently, a delay in supplying oil to the bearings is experienced, which may damage or cause premature failure of the bearings.
The present invention is directed to overcoming the aforementioned problems associated with a compressor oil delivery system, wherein it is desired to provide improved venting of the axial oil passageway in a crankshaft to prevent slow oil flow rates therethrough.